1. Field of the Invention
The present invention relates to a pattern inspection method and apparatus, and, in particular, to an inspection method and apparatus of a circuit pattern with an auxiliary pattern. The circuit pattern is a circuit pattern formed in a mask or the like and used in manufacturing of a semiconductor device.
Recently, high-density integration of semiconductor devices has been developed. As a result, circuit patterns has become finer. As shown in FIG. 1, when using a mask of a pattern of rectangles 10 and performing an exposure, a pattern 11 is formed on a wafer. Due to limitations of resolution of an exposure device, as pattern becomes finer, the rounded pattern shapes 11 occur. When such a phenomenon occurs in a circuit pattern, the corners are rounded. As a result, although electrical connection is performed, it is likely that problems in circuit characteristics will occur.
In order to solve this problem, that is, in order to form a circuit pattern according to design, as shown in FIG. 2, a technique of adding an auxiliary pattern 12 has been used. The auxiliary pattern 12 includes small rectangles, each of which is positioned near a respective corner of the rectangles of the pattern 10. As a result of adding the auxiliary pattern 12, a pattern 13 formed on a wafer is approximately rectangular.
In order to perform inspection as to whether or not defects are present in a circuit pattern including an auxiliary pattern, a pattern inspection method which considers the presence of the auxiliary pattern is needed.
2. Description of the Related Art
Up to this time, inspection of a circuit pattern including an auxiliary pattern has been performed by the same method as that for an ordinary circuit pattern not including an auxiliary pattern. Specifically, as shown in FIG. 3, an image of a pattern of a mask is recognized in a process 20. Thereby, a recognized image 23 including a pattern image 21 and an auxiliary pattern image 22 is obtained. On the other hand, design data including the auxiliary pattern is copied in a process 25. Then, in a process 26, the design data is converted into inspection data which is suitable for conducting inspection of the circuit. Then, in a process 27, the inspection data is converted into an image, and thus, an inspection image 28 including a pattern image 21A and a auxiliary image 22A is obtained. In a process 29, the recognized image 23 is compared with the inspection image 28, and thus, it is determined whether or not defects are present in a circuit pattern of the mask.
The design data which is converted in the process 26 is design data including the auxiliary pattern. The amount of data of this design data is several times larger than the amount of data of the ordinary design data not including the auxiliary pattern. As a circuit pattern becomes finer as mentioned above, the amount of data of the ordinary design data not including the auxiliary pattern increases. Accordingly, the amount of data of the design data including the auxiliary pattern is enormous. As a result, a very long time is required for the data conversion in the process 26, and thus, a very long time is required for the pattern inspection.
Further, due to limitation of data processing capability of the pattern inspection apparatus, as a circuit pattern becomes finer, the petter inspection is performed by dividing one mask into a plurality of divisions and data processing is performed. In such a situation, because the amount of data increases when design data including the auxiliary pattern is processed as mentioned above, it is necessary to divide one mask into an increasing number of divisions. Thereby, a longer time is required for the pattern inspection.
Further, because each rectangle of the auxiliary pattern is very small in comparison to the ordinary pattern, the auxiliary pattern may result in false defects in the pattern inspection. Thus, reliability of the pattern inspection is degraded.